1. Field of the Invention
The present invention relates to an imaging apparatus, imaging apparatus control method, and computer program. More particularly, the present invention relates to an imaging apparatus, imaging apparatus control method, and computer program, which perform focus control.
2. Description of the Related Art
With a great number of current imaging apparatuses such as still cameras, video cameras, and so forth, an auto-focus (AF) mechanism is implemented, which automatically focuses on a subject. For example, with focus control based on contrast measurement employed for many cameras, a focus position is determined by determining whether the contrast of imaged data obtained through a lens is high or low. That is to say, a position where the contrast intensity of an image becomes the maximum is detected while moving a focusing lens, and this position is regarded as a focus position. Note that a range where the focusing lens is moved is referred to as a scan range, and lens driving is typically performed with a range between the near side and the infinity side as a scan range.
Further, a great number of cameras are employed, which have a focus preset function whereby shooting can be performed by rapidly moving a lens to a focus preset position set by a photographer beforehand. For example, with Japanese Unexamined Patent Application Publication No. 2004-294570, and Japanese Unexamined Patent Application Publication No. 2006-64842, a camera having the focus preset function is described. Also, with Japanese Unexamined Patent Application Publication No. 2004-53722, a camera has been disclosed wherein subject distances which a user intends to shoot can be preset by being assigned to multiple buttons.
Employing the focus preset function enables shooting to be started by rapidly moving a lens to a predetermined position, and accordingly, the shooting start timing can be sped up as compared to the case of employing the auto-focus (AF) function.
With shooting employing auto-focus (AF), lens driving is performed with a range between the near side and the infinity side as a scan range, which results in a problem that it takes time to determine a focus position. Also, for example, in a case wherein there is a wire net in front, an animal exists on the other side thereof, and shooting of the animal is attempted, there is a possibility that a contrast peak will be detected in both of the wire net and animal with auto-focus processing, and a photo focused on the wire net is shot, which is not what the user intended.
With Japanese Unexamined Patent Application Publication No. 2006-349744, there has been proposed a method for restricting a scan range of AF to separate multiple subjects as an arrangement for solving such a problem. However, in the case of employing this method, there is a possibility that separation of multiple far and near subjects is not performed well at a zoom position (focal distance) of which the depth of field is deep, such as the wide angle side, and shooting is executed while focusing on a subject other than a target subject. Note that “depth of field” is an in-focus range available before and after one focus position (point of focus), and a state wherein this range is wide is referred to that the depth of field is deep. In general, the depth of field is deep in a case wherein the optical zoom is at the wide angle side, and the depth of field is shallow at the telescopic side.